High Breaking MCB AC Electrical Miniature Circuit Breaker Wsb7-63 MCB 3p

The "high breaking" designation means this 3-pole version is rated to safely interrupt a larger prospective short-circuit current than a standard-duty MCB. It uses optimized arc-splitting chambers, robust contact materials and a stronger operating mechanism to clear high-magnitude faults quickly, making it suitable for feeders close to a transformer or high-capacity supply.

A 3-pole MCB protects and switches the three phase conductors (L1, L2, L3) of a three-phase three-wire circuit, with no neutral pole. All three poles open simultaneously so that a fault on any phase disconnects the whole load. It is wired into a three-phase distribution board with the three phases on the input terminals and the three phase outputs going to the three-phase load.

Three-phase motors, pumps, compressors, heaters and balanced commercial loads must be switched together to avoid single-phasing, where losing one phase forces the motor to overheat. A 3P MCB trips all poles on an overload or short circuit, providing coordinated phase protection and safer isolation than three independent single-pole breakers.

Size the breaker to the full-load current of the three-phase load, using the formula I = P / (√3 × U × cosφ) to estimate the rated current, then choose the nearest standard WSB7-63 rating (up to 63 A) above that value. The breaker should trip before the cables overheat, so cable cross-section must also be matched to the breaker rating.

Most three-phase motor and compressor loads use a C curve (magnetic trip at 5–10 In), which tolerates normal motor starting current but still trips on short circuit. Heavy inrush loads such as transformers, welding sets or large motors may require a D curve (10–20 In), while purely resistive three-phase heating can use B or C depending on inrush.

The thermal trip uses a bimetal that heats and bends under sustained overload, giving an inverse-time delay so that small overcurrents ride through for a defined time before tripping. The magnetic trip is an electromagnet that releases instantly when current reaches the curve threshold, clearing short circuits within milliseconds. Together they provide overload and short-circuit protection in one device.

WSB7-63 breakers are assembled and tested on automated production lines that perform 100% electrical and mechanical checks, including contact resistance, tripping current calibration and mechanical endurance. Automated assembly reduces human variation and ensures consistent breaking capacity, tripping curve accuracy and batch-to-batch reliability.

Yes. The WSB7-63 series is manufactured to IEC 60898-1 for AC miniature circuit breakers and carries CE marking, demonstrating compliance with relevant European health, safety and environmental protection directives. Type tests cover tripping limits, short-circuit endurance, impulse voltage and abnormal heat.

Typical uses include three-phase motor branch protection, commercial air-conditioning and chiller feeds, three-phase distribution sub-mains, machine tool control panels, and incoming protection for small three-phase commercial panels where the available short-circuit level is high. Its 35 mm DIN-rail form factor lets it fit standard modular distribution boards.

First check whether it trips immediately on switch-on (suggesting a short circuit or earth fault downstream) or after running for a while (suggesting overload). Inspect the load current with a clamp meter, verify the cable size, look for a failed motor or locked rotor, and confirm the tripping curve matches the load. If the breaker trips correctly but the load is genuinely overloaded, reduce the load or upsize the circuit and cables together.